异甘草素分子器件输运性质的第一性原理研究

First-principles study on electronic transport in molecular devices of Isoliquiritigenin

基于密度泛函理论和非平衡格林函数相结合的计算方法,研究了异甘草素分子以不同方式耦合到金电极上时,其耦合程度与结构的伏安特性关系。研究表明,异甘草素分子能够与金电极形成良好的耦合;无论以何种方式耦合,所构成分子器件的电流随电压的增大先增大后减小,即存在负微分电阻效应。分子两端分别通过碳和氧原子与金电极耦合的分子结出现负微分电阻效应所需的电压小于两端分别通过硫原子和探针与金电极耦合的分子结;通过对比发现,在电压小于1.56 V时,分子两端分别通过碳和氧原子直接与金电极耦合的分子结的电阻较小,导电能力强。

By applying first principles density functional theory in combination with nonequilibrium Green＇s function,we investigated the relationship between the degree of coupling and the voltage characteristics of structure of the Isoliquiritigenin molecular device when it was coupled to the Au electrodes by different ways.The results showed that the two kinds of coupling mode had a good coupling with Au electrode.Regardless of the coupling,with the increase of voltage,the current firstly increased and then decreased,which meaned that it had a negative differential resistance effect.The voltage（as required） for the negative differential resistance of molecular junctions shaped by a carbon atom and an oxygen atom coupled to the Au electronic on both ends of the molecule was less than that of the molecular junctions shaped by a sulfur atom and a gold probe.By comparison,we found that the junctions shaped by coupling a carbon atom and an oxygen atom with the Au electronic had resistance at the 1.56 V,that is to say,it had good conductivity.